im not sure what is happening please help.

ok im not a computer bod just a music fan..ive had Itunes for a few months and recently tried to download a new update which it required me to do....during the download everything crashed...I lost my Itunes from the computer ..so we reinstalled...everything on my playlists was there as before and the account info was as before...but now whan i purchase any music i get charged twice the cost each item. is it possible that on my computer i have two accounts ?? any ideas?